Use depth control whenever fish are feeding below your presentation, or current carries the fly past useful water before it sinks. Begin with a particular edge, lane or patch of visible activity. Casting farther is only useful if you can manage the line that comes with it.

A short test cast teaches more than a catalogue label. Watch how the line settles, how the fly behaves on a pause and how quickly the current bows the line. Repeat the presentation before changing it, so you know which adjustment made the difference.

A floating line is a useful starting point for surface flies and shallow work. The leader and fly can still sink below it. A weighted fly does not make the floating portion disappear beneath the surface.

An intermediate line sinks below the surface and can help keep a subsurface fly from being pulled up through chop. It is a versatile option for shallow submerged presentations, but its actual depth depends on the sink time, current and retrieve.

A sinking line or sinking head reaches deeper water more readily. Match it to the rod and the presentation. Line weight and sink rate are different things; do not assume the heaviest line is the fastest sinking one. FlyLife’s line-type guide explains the distinction.

The three panels show those behaviours, not three measured fishing depths. None supplies a depth scale or a countdown that works in every current. Choose leader length and strength for the fly and target, and make sure the fly turns over without a tangled landing.

Cast a manageable length and begin counting as the fly lands. Take up loose line without immediately dragging the fly towards you. Start the retrieve after the chosen count and keep that count consistent for the next cast.

Point the rod along the line with the tip low. Use the line hand to make the retrieve, watching for a belly that separates your hand from the fly. Try a steady rhythm first, then vary the length of the pulls or add pauses. A pause may let a weighted fly fall while its materials continue moving.

If you keep touching bottom, shorten the sink time or use a shallower presentation. If the fly seems to be riding above the intended lane, allow more settling time, change the cast angle or use a more suitable line. Bottom contact is a clue, not a depth reading, and it is unnecessary where you can already see the fly and fish.

In current, try an angle that gives the fly time to sink before the line comes tight. Shape the line during the cast if needed; mending explains why a submerged line is harder to reposition. Boat movement also changes the presentation. Judge the fly’s movement relative to the water, not simply the speed of your hand.

Change one variable at a time. Keep a productive count and retrieve rhythm while exploring adjacent water; restart the test when the current or position changes.

Treating a printed sink rate as a depth gauge. Current, leader, fly and retrieve alter the result. Test the whole setup.

Stripping hard immediately after landing. You remove the sinking time you needed. Let the fly settle under control.

A long submerged belly. Shorten the cast and improve the angle. Pulling harder does not necessarily restore direct contact.

The same retrieve for every fly. Check the action where you can see it. A baitfish pattern and a weighted prawn need not move alike.

Assess the fishing position before testing depth. NSW DPIRD’s fishing safety guidance recommends checking weather and water conditions and wearing a lifejacket when boat fishing. For northern waters, also consult the relevant authority’s crocodile guidance before selecting a shore position; the NT Government provides Be Crocwise advice.

Check the current jurisdiction rules, local access and marine restrictions. A sinking-line illustration cannot tell you whether a bank, flat or channel is safe to enter.